The distribution and dynamics of aggregates in the aquatic environment play an important role in the modelling of biogeochemical processes. Previous work on aggregates in the ocean (e.g. sedimentary 'marine snow' particles), which vary in size from tens of microns to several millimetres, has used electronic counting or conventional photography coupled with image analysis. Here we describe a non-destructive in situ approach by use of holographic mensuration, hologrammetry, that affords greater scope and higher accuracy for the enumeration, sizing, and spatial distribution determination of aggregate particles. By means of two complimentary techniques, in-line and offaxis transmission holography, we present the initial experiments conducted in our laboratory and discuss the preliminaiy results from real image analysis.